Appendix D:

Air Quality

Erratum

Point Defiance Bypass 

Project

Air Quality Discipline 

Report Erratum

November 2012

Table of Contents

Chapter 1 – Introduction.................................................................................................................... 1

What is the purpose of this erratum?............................................................................................ 1

Why do the project-level conformity results need to be updated? ................................................ 1

Chapter 2 – Methodology.................................................................................................................. 2

Which intersections were included in the revised project-level conformity analysis? ................... 2

How were the intersections analyzed?......................................................................................... 3

Chapter 3 – Affected Environment .................................................................................................... 4

Chapter 4 – Project Effects ............................................................................................................... 5

What were the results of the revised analysis? ............................................................................ 5

Conformity Statement................................................................................................................... 5

Chapter 5 – Recommended Minimization Measures......................................................................... 7

Are any additional mitigation measures proposed?...................................................................... 7

References........................................................................................................................................ 8

Table of Exhibits

Exhibit 1. Level of Service and Delay for the At-Grade Intersections (PM Peak Hour) ..................... 2

Exhibit 2. Maximum Predicted CO Concentrations at the Intersection of North Thorne Lane 

Southwest and I-5 Northbound Ramps ............................................................................. 6

Point Defiance Bypass Project November 2012

Air Quality Discipline Report Erratum Page i

Chapter 1 – Introduction

What is the purpose of this erratum?

This erratum updates the results of the project-level carbon 

monoxide (CO) conformity analysis performed for the Point 

Defiance Bypass Project (Project) that were presented in the 

Project’s Air Quality Discipline Report, dated September, 2012 

(WSDOT 2012).

Why do the project-level conformity results 

need to be updated?

The results of the original air quality analysis conducted for the 

Project were presented in the Draft Air Quality Discipline Report, 

dated October, 2011 (WSDOT 2011a). The intersections selected 

for project-level CO) conformity analysis (also called a hot spot 

analysis) were based on an operational ranking of project-affected 

intersections based on level-of-service (LOS) and average 

intersection delay in seconds. The data upon which the intersection 

selection was made was contained in Attachment A of the Project’s 

Draft Transportation Discipline Report, dated December, 2011 

(WSDOT 2011b).

Revisions to the transportation analysis between the date of the 

Draft Air Quality Discipline Report (October, 2011) and the Draft

Transportation Discipline Report (December, 2011) indicated that 

the intersections with the worst LOS changed slightly. This change 

meant that not all the intersections analyzed in the CO hot spot 

analysis were the worst performing intersections and that there 

were intersections that had a greater potential to impact continued 

compliance with the CO National Ambient Air Quality Standards 

(NAAQS) than those analyzed for the Project. Therefore, the hot 

spot analysis needed to be updated to include the more congested 

intersections to demonstrate compliance with the project-level 

conformity requirements for projects in CO maintenance areas.

Point Defiance Bypass Project November 2012

Air Quality Discipline Report Erratum Page 1
Chapter 2 – Methodology 

The following updates Chapter 2 – Methodology of the September 

2012 Air Quality Discipline Report.

Which intersections were included in the 

revised project-level conformity analysis?

The original project-level conformity analysis was performed on 

the following intersections:

• East “D” Street and East 26th Street 

• Barksdale Avenue and Northbound I-5 Ramps

• Berkeley Street and Union Avenue

Attachment A of the Project’s Draft Transportation Discipline 

Report (WSDOT, 2011b) indicates that the three intersections with 

the worst LOS (and hence, most congestion) are:

• East “D” Street and East 26th Street

• North Thorne Lane Southwest and I-5 Northbound Ramps

• North Thorne Lane Southwest and Union Avenue Southwest

Therefore, the project-level conformity analysis was updated to include 

the intersections of North Thorne Lane Southwest and I-5 Northbound

Ramps, and North Thorne Lane Southwest and Union Avenue Southwest.

Exhibit 1 shows the LOS and delay for the three analysis intersections.

Exhibit 1. Level of Service and Delay for the At-Grade Intersections (PM Peak Hour)

2010

Existing Year

LOS/Delay

2030

LOS/Delay

No-Build Build

Intersection Name LOS

Average 

Delay LOS

Average 

Delay LOS

Average 

Delay

East “D” Street and East 26th Street B 10.7 E 72.6 E 72.8

North Thorne Lane Southwest and Northbound

I-5 Ramps B 17.2 F 91.3 E 74.8

North Thorne Lane Southwest and Union Street F 52.4 F 182.9 F 188.0

Source: HDR Traffic Data Submittals

Notes: Delay is shown in seconds

November 2012 Point Defiance Bypass Project

Page 2 Air Quality Discipline Report Erratum
How were the intersections analyzed?

The project-level conformity analysis for the two additional intersections 

was performed using the same procedures as the previous analysis. The 

analysis used the WSDOT WASIST model (version 2.0). WASIST is a 

Windows-based screening model used for determining worst-case CO 

concentrations at signalized intersections throughout the State of 

Washington. WASIST uses readily available data in a user-friendly 

application to make a conservative estimate of project-related CO levels. 

This is done by using a combination of worst-case conditions that, when 

occurring simultaneously, produce the highest levels of CO. If the results 

from WASIST do not violate NAAQS for CO, the impact from any other 

combination of conditions would also be below the standards and no 

further modeling is required.

Traffic data for the revised project-level conformity analysis were 

obtained from Appendix D of the Proposed Signal Phasing/Timing and 

Traffic Operations Technical Memorandum (without Cross-Base 

Highway) (HDR, 2011). Traffic data used in the analysis are included in 

Attachment A. Turning movement traffic volume data were not available 

for the intersections of North Thorne Lane Southwest and I-5 Northbound

Ramps, and North Thorne Lane Southwest and Union Avenue Southwest

in the project year of opening (2017), so the WASIST model was 

conservatively run with 2017 emission factors and 2030 traffic volumes to 

demonstrate compliance in 2017 where appropriate. 

Point Defiance Bypass Project November 2012

Air Quality Discipline Report Erratum Page 3
Chapter 3 – Affected Environment

There were no updates to Chapter 3 – Affected Environment of the 

September 2012 Air Quality Discipline Report.

November 2012 Point Defiance Bypass Project

Page 4 Air Quality Discipline Report Erratum
Chapter 4 – Project Effects

The following updates Chapter 4 – Project Effects of the 

September 2012 Air Quality Discipline Report.

What were the results of the revised analysis?

The Project is not anticipated to create any new violations, nor increase 

the frequency of an existing violation of the CO standard at projectaffected, signalized roadway intersections; it would conform with the 

purpose of the current SIP and the requirements of the federal CAA and 

the Washington CAA.

A project-level conformity analysis was performed for the existing year 

(2010) and for all the alternatives of the year of opening (2017) and the 

horizon year (2030), including the No Build Alternative where the 

intersection LOS was at D or below.

For the intersection of North Thorne Lane Southwest and Union Avenue 

Southwest, traffic volumes under the existing, No Build, and Build 

Alternatives were low enough that the intersection passed the initial 

WASIST screen and a full WASIST hot spot analysis was not required.

For the intersection of North Thorne Lane Southwest and I-5 Northbound

Ramps, traffic volumes were high enough that full WASIST analysis was 

required.

The results for the worst-case receptor at this intersection were below the 

1-hour average NAAQS for CO of 35 ppm and below the 8-hour average 

standard of 9 ppm under all modeled conditions. Exhibit 2 provides the 

maximum CO concentrations of WASIST Model Outputs.

WASIST output files for both intersections are included in Attachment B.

Conformity Statement

This erratum provides additional information that should be considered in 

addition to the evaluation of potential air quality emissions from 

construction and operation of the project presented in the Air Quality 

Discipline Report. The revised project-level conformity analysis confirms 

Point Defiance Bypass Project November 2012

Air Quality Discipline Report Erratum Page 5
the conclusion presented in the Air Quality Discipline Report that the 

Project is not expected to:

• Cause or contribute to any new violations of the NAAQS;

• Increase the frequency or severity of any existing violation of the 

NAAQS; or

• Delay the timely attainment of the NAAQS.

Exhibit 2. Maximum Predicted CO Concentrations at the Intersection of North

Thorne Lane Southwest and I-5 Northbound Ramps

Alternatives Intersection

Averaging Time

North Thorne Lane Southwest and I-5 Northbound Ramps

1 hr 8 hr

2010 (Existing) 4.9 4.3

2017 No Build 4.5 4.0

2017 Build 4.5 4.0

2030 No Build 4.3 3.9

2030 Build 4.3 3.9

Notes: Concentration values are in parts per million. The one-hour NAAQS for CO is 35 ppm and for the 

eight-hour CO is 9 ppm. A background ambient CO concentration of 3 ppm was used in the WASIST 

modeling.

November 2012 Point Defiance Bypass Project

Page 6 Air Quality Discipline Report Erratum
Chapter 5 – Recommended 

Minimization Measures 

The following updates Chapter 5 – Recommended Minimization 

Measures of the September 2012 Air Quality Discipline Report.

Are any additional mitigation measures 

proposed? 

The results of the revised air quality study indicate that no exceedance of 

the NAAQS will occur as a result of Project implementation. Therefore no 

additional mitigation measures are required or recommended.

Point Defiance Bypass Project November 2012

Air Quality Discipline Report Erratum Page 7
References

HDR Engineering. 2011. Proposed Signal Phasing/Timing and Traffic Operations 

Technical Memorandum (without Cross-Base Highway). April, 2011.

Washington State Department of Transportation. 2011a. Point Defiance Bypass 

Project Air Quality Discipline Report. October, 2011. 

Washington State Department of Transportation. 2011b. Point Defiance Bypass 

Project Transportation Discipline Report. December, 2011. 

Washington State Department of Transportation. 2012. Point Defiance Bypass 

Project Air Quality Discipline Report. September2012.

November 2012 Point Defiance Bypass Project

Page 8 Air Quality Discipline Report Erratum
Attachment A – Traffic Data
Appendix D-4b Thorne Lane Existing PM Peak Hour Scenario (4) - VISSIM Simulation Ou

Node Intersection Movement VISSIM Output Volume Movement Delay Avg. Queue Max Queue Avg

D

EBT 157 46.4 37 239 3EBR 1 14.3 14 186 1WBL 297 0.9 1 60 WBT 110 1.4 1 60 NBL 7 120.1 193 682 9NBR 301 122.5 235 736 9All 873 52.4 - - 4EBT 441 28.7 125 203 2EBR 16 35.0 125 203 3WBL 166 2.4 1 23 WBT 54 2.5 1 23 SBL 302 48.3 102 514 3SBT 96 49.4 102 514 3SBR 352 10.0 122 544 All 1426 25.6 - - 1EBL 364 3.5 5 66 EBT 378 0.9 5 66 WBT 213 52.5 94 712 4

WBR 696 19.7 94 712 

2a North Thorne Ln & Union Ave2b North Thorne Ln & I-5 SB Ramp

20101111.AR.Thorne-Lane_2010-PM-MOEs-20runs.xlsm

WBR 696 19.7 94 712 NBL 6 82.1 16 171 7NBT 2 78.5 16 171 7NBR 167 24.7 27 184 1All 1827 17.2 - - 

Network Summary All 4126 27.5 - - 1

2c North Thorne Ln & I-5 NB Ramp

20101111.AR.Thorne-Lane_2010-PM-MOEs-20runs.xlsm
Appendix D-10b Thorne Lane 2030 No-Build PM Peak Hour Scenario (10) - VISSIM Simulation 

Node Intersection Movement VISSIM Output Volume Movement Delay Avg. Queue Max Queue Avg

D

EBT 109 63.4 39 227 5EBR 9 37.9 14 174 1WBL 261 0.6 1 31 WBT 118 1.2 1 31 NBL 7 434.4 1109 1345 3NBR 328 431.9 1162 1399 3All 833 182.9 - - 1EBT 429 30.7 132 200 2EBR 7 34.3 132 200 3WBL 195 4.6 3 45 WBT 89 4.6 3 45 SBL 372 94.5 245 1018 7SBT 19 88.4 245 1018 6SBR 290 17.9 269 1047 All 1402 40.7 - - 3EBL 310 3.5 5 53 EBT 491 1.1 5 53 WBT 278 117.3 427 1188 6WBR 737 65.5 427 1188 

NBL 6 384 6 790 1184 2

2c North Thorne Ln & I-5 NB Ramp

2a North Thorne Ln & Union Ave2b North Thorne Ln & I-5 SB Ramp

20110202.TW.Thorne-Lane_2030NB-PM-MOEs-20runs.xlsm

NBL 6 384.6 790 1184 2NBT 6 370.3 790 1184 2NBR 315 345.4 803 1197 1All 2144 91.3 - - 3

Network Summary All 4378 92.5 - - 5

20110202.TW.Thorne-Lane_2030NB-PM-MOEs-20runs.xlsm
Appendix D-11b Thorne Lane 2030 Build with Train PM Peak Hour Scenario (11) - VISSIM Simul

Node Intersection Movement VISSIM Output Volume Movement Delay Avg. Queue Max Queue Av

D

EBT 112 42.2 27 190 EBR 9 23.7 12 154 WBL 261 1.5 3 77 WBT 119 2.5 3 77 NBL 6 520.8 1176 1397 4NBR 287 489.9 1175 1396 4All 796 188.0 - - 1EBT 393 2.3 2 82 EBR 7 0.1 2 82 WBL 208 6.8 6 220 WBT 94 7.4 6 220 SBL 370 59.4 149 745 SBT 19 61.6 149 745 SBR 286 57.0 149 745 All 1376 30.9 - - EBL 282 12.4 30 266 EBT 480 2.3 30 266 WBT 295 69.7 214 1159 

WBR 779 33.6 214 1159 

2a North Thorne Ln & Union Ave2b North Thorne Ln & I-5 SB Ramp

20110411.TW.Thorne-Lane_2030S1-PM-MOEs-20runs-wTrain.xlsm

WBR 779 33.6 214 1159 NBL 7 324.1 752 1184 1NBT 7 307.2 752 1184 1NBR 352 310.0 765 1197 1All 2202 74.8 - - 

Network Summary All 4374 81.5 - - 

2c North Thorne Ln & I-5 NB Ramp

20110411.TW.Thorne-Lane_2030S1-PM-MOEs-20runs-wTrain.xlsm
Attachment B – WASIST Output Files